1. Field of Invention
Various exemplary embodiments relate to a semiconductor memory device and a method of operating the same.
2. Description of Related Art
A semiconductor memory device is classified into a volatile semiconductor memory device and a non-volatile memory device. The volatile semiconductor memory device is classified into a dynamic random access memory and a static random access memory again. The volatile semiconductor memory device has a high read and write rate, but has a disadvantage in that stored contents disappear when an external power supply is blocked. The nonvolatile semiconductor memory device is classified into a Mask Read-Only Memory (MROM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM) and the like. The nonvolatile semiconductor memory device preserves stored contents even though an external power supply is blocked. Accordingly, the nonvolatile semiconductor memory device is used for storing contents to be preserved regardless of the supply of the power.